TR4… Why Queensland’s different

The recent discovery of Panama disease Tropical Race 4 in North Queensland has led to doomsayers predicting the end of the banana industry in Australia. Story by Tony Pattison.

While not discounting the seriousness of the outbreak, there are several factors weighing in favour of the survival of the Australian banana industry, including lessons learnt from outbreaks overseas and the development of international partnerships to help tackle the problem.

The greatest enemy in an outbreak is complacency and denial. This complacency, lack of diagnostic tools, reluctance to admit the presence of the disease and inability to change farming practices is why the disease has spread and continues to spread around the world.

Early detection

There are three main factors in favour of the Australian banana industry being able to manage and survive the outbreak of Tropical Race 4.

The first is early detection and recognition of the disease.

While there is more work to be done determining the extent of the outbreak, the fact that we recognise the disease is present, and have acted, puts us ahead of most international outbreaks of the Tropical Race 4.

The fungal pathogen is easily moved in soil and in planting material, which means that early detection and quarantining can slow the spread of the disease to other areas.

It is still too early to determine if the Tully site where the first detection was made was the original site of infection, but this detection is now contained.

In other outbreaks of TR4, the recognition of the disease has often taken years, either through denial or through lack of diagnostic capabilities, which has meant the disease had spread from the initial site.

On-farm biosecurity

The second factor working in the favour of the Australian banana industry is the knowledge of on-farm biosecurity.

While not every farm may implement on-farm biosecurity, the concept was not new for banana growers.

In outbreaks of TR4 overseas, the concept of restricting the movement of people though farms was difficult or impossible to implement.

Many of the on-farm biosecurity arrangements in place in overseas outbreaks occurred after the disease had reached the farm, with little knowledge of what to do to disinfect machinery and footwear.

The implementation of on-farm biosecurity is now up to individual farms, but there are resources available for Australian banana farmers including checklists, product recommendations, guides and signage. Overseas outbreaks did not have these resources.

Farm practices

The third factor in the favour of the survival of the north Queensland banana industry is the way bananas are grown.

Over the past 20 years there has been a concerted effort to improve the farming practices to reduce inputs on-farm and protect the environment off-farm.

The subtle practices of grassed interrows, reduced soil pesticide applications, lower nitrogen application and soil pH management all contribute to improve the biodiversity in the soil.

In the soil, the Fusarium fungus that causes the Panama disease requires carbon to grow.

The fungus obtains its carbon by infecting the plant, surviving on alternate host plants or undecomposed organic matter in the soil.

pH and organic matter

By increasing the biological diversity in the soil there is greater competition between other soil organisms and the Fusarium fungus. As only one to 10 per cent of soil organisms can be cultured from the soil, the best tactic to improve soil biological diversity is to encourage the organisms naturally occurring in the soil.

By having a neutral soil pH, greater recycling of organic matter (such as banana trash) and an increase in the diversity of different plant species on the soil, each with their own complement of microorgansims around their roots, the competition in the soil for carbon increases.

Soil organisms that compete with pathogens for carbon are usually slower growing, but commonly produce anti-microbial compounds to protect their spot in the soil.

The anti-microbial compounds produced come at an energy cost to the organisms and therefore they tend to be slower growing, requiring stable environments to prosper. This is where the improvements in farming practices in north Queensland become important.

Not the end

Groundcovers in the row, the continual breakdown of banana trash, frequent but smaller fertiliser applications, reduced pesticide applications, good irrigation systems and neutral soil pH, all create a more stable soil environment to promote soil biodiversity.

By contrast, outbreaks of TR4 in commercial plantations overseas have typically occurred where the soil is kept clean of vegetation, farm inputs tend to be higher of both fertilisers and pesticides and soils tend to be more acidic. Increased soil biodiversity will not stop the disease on infected sites, but it tips the balance away from the fungus.

The identification of TR4 in north Queensland is a serious threat to banana production in the region.

However, it will not be the death of the industry as predicted by some, as long as the industry continues to act swiftly to recognise infected plants, isolate infected areas, implement on farm biosecurity practices to reduce the movement of the fungus and improve soil management, with a focus on creating a stable soil environment for a biologically diverse microbial community.